1. Field of the Invention
The present invention relates to an optical input device and, more particularly, to an optical input device, in which an ON/OFF time of a light source is actively set according to an ON/OFF time of a shutter in the case of collecting light from the light source to obtain an image to detect movement.
2. Description of the Related Art
A human interface device (HID) generally refers to all the devices which support a human to conveniently process an interface with a computer or its peripherals. The HID may be sorted into a keyboard, a mouse, a wireless remote controller, and keypad for a mobile phone, a computer, a digital camera, television, and so forth.
In particular, the invention is directed to an optical input device among the HIDs, which collects light from a light source, obtains an image, calculates movement, and outputs the calculated result.
An optical mouse stands for the optical input device, and is designed so that a light source illuminates light on a subject (workable surface) with which the mouse comes into contact, and then an image sensor reads movement of the reflected light to move a cursor.
The optical mouse of this type has a variety of kinds. The first is a wired optical mouse using power of the computer and PS2/USB (Universal Serial Bus) for transmission of data.
The second is an RF (Radio Frequency) optical mouse using its built-in battery as a power source and an additional RF transmitter for data transmission.
The third is an IR (Infrared) optical mouse using its built-in battery as a power source and including an additional data transmission light source and a transmission module to transmit the data of the optical mouse on the basis of an IR mechanism.
In this manner, the optical mouse applied in the various types is designed, as shown in FIG. 1, so that light 7 emitted from a light source 8 is reflected from a worktable surface 2, and the reflected light 6 passes through a lens 5 to be inputted into an image sensor 3.
The optical mouse 1 obtains an image of the worktable surface 2 using a quantity of light 6 collected in the image sensor 3, and calculates the movement of the optical mouse by comparing the obtained image with an image formed in the previous sample period.
In this case, when the movement is sensed, the optical mouse unconditionally keeps the light source 8 in an on state as in FIG. 2. However, when the movement is not sensed, the optical mouse causes the light source 8 to be turned on/off at constant intervals.
And the optical mouse controls a time when the image sensor is shuttered on as in FIGS. 3A and 3B according to brightness of the worktable surface in order to exactly read an image of the worktable surface. The optical mouse causes a quantity of the light incident on the image sensor 3 to have a constant value at all times by decreasing the time when the image sensor 3 is shuttered on in the bright workable surface and by increasing the time when the image sensor 3 is shuttered on in the dark workable surface.
In FIGS. 3A and 3B, a shutter on period refers to a period where the image sensor 3 reads the image of the worktable surface 2 through the quantity of the incident light, while a shutter OFF period refers to a period where the image sensor 3 does not read the image of the worktable surface 2.
In this manner, the optical mouse according to the prior art turns on the light source without any condition when its movement is sensed.
Therefore, the optical mouse according to the prior art is operated by on operation of the light source even in the period where it is unnecessary to be operated by on operation of the light source, such as the shutter OFF period where the image sensor does not read the image of the worktable surface, thus resulting in undesired waste of electric power and reduction of energy efficiency.
For this reason, when the optical mouse is either the wired optical mouse connected to a device such as a notebook computer sensitive to consumption of the electric power or the IR or RF optical mouse using its built-in battery as a power source, undesired consumption of the electric power is generated, so that there is a trouble of frequently substituting the battery.